In a light-emitting device in which a plurality of light-emitting diode elements (hereinafter referred to as LED elements) of a high output type for illumination are mounted, semiconductor devices for communication or control or the like in which various electronic elements are densely mounted, much currents flow at the time of the light emission of the LED elements or a high speed drive, or in accordance with a load capacity to be driven. Thereby, high-temperature heat is generated. Therefore, in a conventional mounting substrate formed of a resin material of an epoxy substrate and so on, there are problems such as low heat resistance and low heat dissipation, deterioration promotion of the mounting substrate due to heat generation, and characteristic change or malfunction of the mounted LED elements or other electric elements.
To improve such problems caused by heat, in the light-emitting device for illumination or the semiconductor device of the high density, a metallic mounting substrate formed of an aluminum material having a lightweight and excellent in heat resistance and heat dissipation is often used (see, for example, Patent Literatures 1 to 3).
By the way, as a metallic mounting substrate used for such as conventional light-emitting devices for illumination, a mounting substrate including an aluminum substrate having a surface which has an oxide film formed of alumite processing and a reflection layer containing silver of a high light reflectance and formed on the surface of the aluminum substrate is often used. The mounting substrate is adapted to respond to a request of light reflectivity in addition to heat resistance and heat dissipation to a plurality of LED elements mounted on the reflection layer.